DE102022204034A1 - Compensation for springback in the multi-stage production of formed parts - Google Patents

Abstract

The invention relates to a computer-aided method for determining springback-compensated effective geometries for pressing tools, to a method for producing a pressing tool, to a method for producing a pressed part and to a computer program product. Use in computer-aided simulation-based production planning

Description

FIELD OF APPLICATION AND STATE OF TECHNOLOGY

The invention relates to a computer-aided method for determining springback-compensated effective geometries for pressing tools that are intended for producing a pressed part by means of a sequence of several successive pressing operations, to a method for producing a pressing tool, to a method for producing a pressed part and to a computer program product.

The production of pressed parts made of sheet metal, in particular body parts for vehicles, is usually carried out using multi-stage pressing processes that have a sequence of several consecutive pressing operations. Here, a semi-finished product in the form of a sheet metal blank is usually first formed using a forming process, for example by deep drawing or body drawing or stamping, and then further processed in further pressing operations. The further pressing operations can, for example, provide for further drawing processing, trimming, resetting, setting, reshaping or the like. The further pressing operations are also referred to below as subsequent operations and the sub-processes that take place on the workpiece are collectively referred to as pressing processing.

The tool production of a pressing tool typically takes place in numerous stages. A comprehensive presentation can be found in the specialist book: A. Birkert, S. Haage, M. Straub: “Forming production of complex body parts - design of drawing systems”, Springer ViewegVerlag (2013), Chapter 5.9. A fundamentally functional pressing tool is initially produced up to the stage of so-called tool training and tool testing. This is followed by the tool correction stage, which also includes springback compensation. Springback compensation includes measures that are carried out on the fundamentally functional pressing tool in order to ensure that, in addition to tear-free and wrinkle-free producibility, the dimensional and shape accuracy of the pressed part to be produced is in accordance with the requirements despite elastic springback.

The measures to be taken as part of springback compensation are necessary because, in practice, complex pressed parts cannot be manufactured straight away within specified dimensional and shape tolerances with tool zero geometry. Tolerance deviations on the first pressed part falling on the tool have a variety of causes, both in relation to an absolute value of the deviation and the spread of the deviation across several pressed parts. The dimensional and shape deviations mentioned are predominantly the result of an elastic springback of the pressed part after the tool has been opened and/or after the workpiece has been removed from it. It is generally known that the elastic springback of the pressed part causes considerable costs in tool production. Not insignificant proportions of the total costs of tool production have to be spent in order to adapt the basically functional pressing tool as part of the tool correction to compensate for the geometric deviations of the pressed part caused by springback.

• Unter „Nullgeometrie“ soll diejenige Geometrie des Werkstücks verstanden werden, die man in der betreffenden Pressoperation des mehrstufigen Pressprozesses zu erreichen gedenkt. Ein Presswerkzeug, das auf einer CAD-Sollgeometrie des herzustellenden Werkstücks (d.h. die Nullgeometrie) modelliert wird, wird auch als „Nullwerkzeug“ bezeichnet. In einem solchen (nicht kompensierten) Werkzeug sind die Werkzeug-Nullgeometrie und die Werkstück-Nullgeometrie identisch. Unter „Korrekturgeometrie“ ist eine korrigierte, also vereinfacht ausgedrückt eine zum Ausgleich der elastischen Rückfederung „überbogene“ Werkzeuggeometrie zu verstehen. Die Korrekturgeometrie kann auch als „Kompensationsgeometrie“ bezeichnet werden. Die Kompensationsgeometrie weicht zwingend von der in der betreffenden Pressoperation zu erreichenden Nullgeometrie ab, da nach dem Öffnen des Werkzeugs und/oder der Entnahme des Werkstücks aus demselben eine elastische Rückfederung des Werkstücks zu verzeichnen ist. Mit „Rückfederungsgeometrie“ wird die nach dem Öffnen des Werkzeugs und/oder nach der Entnahme des Werkstücks aus demselben sich ergebende Werkstückgeometrie bezeichnet. Die „Rückfederungsgeometrie“ kann auch als (elastische rückgefederte) Ist-Geometrie bezeichnet werden. Die Rückfederungsgeometrie des Werkstücks soll jedenfalls nach der letzten Pressoperation des mehrstufigen Pressprozesses der angestrebten Nullgeometrie entsprechen. Vereinfacht ausgedrückt sollte eine Korrekturstrategie so beschaffen sein, dass durch eine Ermittlung rückfederungskompensierter Wirkgeometrien der Presswerkzeuge die Herstellung eines Pressteils in Nullgeometrie ermöglicht wird. Dabei kann ein Presswerkzeug, dessen Wirkgeometrie entsprechend angepasst ist, auch als „kompensiertes Werkzeug“ oder „korrigiertes Werkzeug“ bezeichnet werden.

To adapt the pressing tools, there are different correction or compensation strategies in the prior art. These aim - starting from a fundamentally functional pressing tool - to eliminate dimensional and shape deviations of the pressed part after the relevant pressing operation by adapting the tool geometry depicting the pressed part of the relevant pressing operation, so that at the end of the multi-stage pressing process a tolerance-compliant target geometry of the pressed part is achieved becomes. In the context of this application, the target geometry is also referred to as the “zero geometry” of the workpiece. In particular, the following definitions should apply within the scope of this application:

• “Zero geometry” should be understood as the geometry of the workpiece that is intended to be achieved in the relevant pressing operation of the multi-stage pressing process. A press tool that is modeled on a CAD target geometry of the workpiece to be produced (ie the zero geometry) is also referred to as a “zero tool”. In such a (non-compensated) tool, the tool zero geometry and the workpiece zero geometry are identical. “Corrective geometry” is understood to mean a corrected tool geometry, i.e., to put it simply, a tool geometry that is “overbent” to compensate for the elastic springback. The correction geometry can also be referred to as “compensation geometry”. The compensation geometry necessarily deviates from the zero geometry to be achieved in the pressing operation in question, since after opening the tool and/or removing the workpiece from it, an elastic springback of the workpiece is recorded. “Springback geometry” refers to the workpiece geometry that results after opening the tool and/or after removing the workpiece from it. The “rebound geometry”. rie” can also be referred to as the (elastic, spring-back) actual geometry. In any case, the springback geometry of the workpiece should correspond to the desired zero geometry after the last pressing operation of the multi-stage pressing process. To put it simply, a correction strategy should be such that the production of a pressed part in zero geometry is made possible by determining spring-back-compensated effective geometries of the pressing tools. A pressing tool whose effective geometry is adjusted accordingly can also be referred to as a “compensated tool” or “corrected tool”.

The state of the art describes a wide variety of simulation-supported compensation strategies for pressing tools in multi-stage pressing processes.

For example, in the technical article: K. Roll, T. Lemke, K. Wiegand: “Possibilities and Strategies for Simulations and Compensation for Springback”, AIP Conference Proceedings, vol. 778. Melville, NY: American Institute of Physics, 2005, pages 295/302, an overview of several simulation-based compensation strategies is given. The recommendation is made that geometric deviations of the workpiece from the zero geometry should generally be compensated for in the pressing operation identified as the cause. In addition, reference is made to a conference contribution by the same authorship that corresponds to the aforementioned specialist article (LS-DYNA User Forum, Bamberg 2004: “Simulation-supported compensation for springback”).

On the other hand, it is known from the specialist article: A. Birkert et al.: “Optimization of the process robustness of the stamping of complex body parts with regard to dimensional accuracy”, IOP Conference Series: Materials Science and Engineering 418 (2018) 012107, that An unstable positioning of the workpiece on or in the tool can have a significant influence on the robustness and thus the repeatability of multi-stage pressing processes. It was shown that an improved positioning of the workpiece - in addition to other factors mentioned there - can reduce the dimensional variation of the pressed parts. The positioning situation of the workpiece when it is inserted into the tool is also referred to below as the partial position. If the workpiece geometry to be inserted and the receiving effective geometry of the tool differ, this is a so-called workpiece position error.

In the patent specification “Compensation for springback in the multi-stage production of formed parts” ( DE 10 2019 203 082 A1 ) concrete compensation strategies are described which take the partial position, i.e. the positioning of the workpiece, into account in further pressing operations. Care is taken to ensure that the receiving active surface geometry of a further pressing operation corresponds, at least in sections, to the incoming workpiece geometry. The compensation strategies shown there should be generally applicable to any workpiece geometry of a body component manufactured using metal forming. However, with regard to the remaining known compensation strategies, this approach is expected to involve a significant amount of additional time in generating the tool effective surfaces, especially as the number of further pressing operations increases. This is due to the fact that in the usually iterative springback compensation procedure, the simulation process must be interrupted after each pressing operation and the effective area of the following pressing operation must be adapted to the workpiece that arrives with springback.

TASK AND SOLUTION

Against this background, the invention is based on the object of providing a method of the type mentioned at the outset, which enables the most general applicability possible to different multi-stage pressing processes and the production of pressing tools for use in such multi-stage pressing processes, the pressing tools to be produced being designed in such a way that the Pressed parts produced with it are as dimensionally accurate as possible and the multi-stage pressing process is at the same time as robust as possible, with the time required for the process compared to the known prior art in the published publication DE 10 2019 203 082 should be significantly reduced.

To solve this problem, the invention provides a computer-aided method with the features of claim 1. Furthermore, a method with the features of claim 8, a method with the features of claim 9 and a computer program product with the features of claim 10 are provided. Advantageous further developments are specified in the dependent claims. The wording of all claims is incorporated by reference into the content of the description.

The method according to the invention with the features of claim 1 comprises steps a) to e) and step z). Accordingly, the solution according to the invention is not initially complete compared to the prior art Sequence viewed (simulated) as a coherent process. Rather, each pressing operation in the sequence is considered (simulated) individually, with disturbances in the form of avoidable elastic deformation energy being eliminated. Avoidable elastic deformation energy is understood to mean the deformation energy that is already generated when the hold-down device (s) is closed in the pressing operation in question due to the fact that the receiving effective surfaces of the pressing operation in question and the effective surfaces of the hold-down device (s) have a different geometry than the incoming workpiece.

In terms of process technology, this is achieved by the fact that the workpiece arriving in the pressing operation in question (simulatively) has not experienced any springback and is therefore practically of the same geometry in the relevant effective surface areas as the receiving pressing operation. In addition, the complete pressing operation including the (isolated) springback is simulated for all pressing operations. The individual springback results (dimensional deviations) resulting from the pressing operations considered in isolation are then linked together in a suitable manner for all pressing operations in order to obtain a statement about the dimensional deviations to be compensated for in the individual pressing operations. The method according to the invention can be applied to a wide variety of multi-stage pressing processes, so that in particular application-specific, experience-based adaptation of the tools can be largely or even completely dispensed with and the process can be automated. The effective geometries determined using the method according to the invention allow, on the one hand, a largely dimensionally accurate production of the pressed part in question and, on the other hand, at the same time, good robustness and thus repeatability of the multi-stage pressing process are made possible, but compared to the patent specification “Compensation of springback in the multi-stage production of formed parts”. ( DE 10 2019 203 082 A1 ) significantly reduced work and time expenditure.

Step a) involves simulating a first pressing operation of the multi-stage pressing process. In this simulation, a virtual workpiece that represents the real pressed part is formed using a virtual tool that represents a real pressing tool of the multi-stage pressing process. Here, the workpiece is picked up at least in sections on an active surface when it is inserted into the first tool and is then reshaped by the action of one or more active surfaces. The virtual effective surface of the first tool can represent a real effective geometry of the pressing tool in question and is usually based on CAD zero data of the workpiece. In addition to the simulation of the actual forming, step a) also includes a determination of the elastically spring-back geometry of the workpiece, which, as defined at the beginning, can also be referred to as the actual geometry. The springback geometry can be present after a virtual opening of the tool and/or removal of the formed workpiece from the tool. The springback geometry preferably relates to a state of the workpiece that is at least essentially, preferably completely, free of external forces, whereby an influence of gravity on resulting deformations of the workpiece can be taken into account. The simulation according to step a) therefore includes a computer-aided calculation of a deformed and elastically spring-back configuration of the workpiece, this configuration being also referred to as the first spring-back geometry in the context of step a). Computer-aided calculation methods suitable for carrying out step a) are generally known as such in the prior art and therefore do not require any further description. These include primarily, but not exclusively, finite element methods.

Step b) provides for simulating the at least one subsequent operation of the multi-stage pressing process using the at least one further tool. The simulation is carried out in a manner corresponding to step a) using a suitable computer-aided calculation method. Deviating from step a), the workpiece is now already in a formed, but not spring-back configuration, namely the first pressed part zero geometry. This is picked up using the active surface of the at least one further tool and processed again using pressing technology. The elastically spring-back configuration that occurs after this machining is referred to as the further spring-back geometry of the workpiece.

Step c) involves determining the geometric deviations of the workpiece. These deviations relate to the desired zero geometry of the workpiece. The deviations are determined by comparing the existing springback geometries with the said zero geometry. The deviation sizes can be a scalar or vector size or field size. The deviation quantities are preferably determined in the form of a displacement vector field between the desired zero geometry and the springback geometries that are now present.

Steps d) and e) involve adjusting the tools, namely the first tool and of the at least one further tool to minimize the previously determined geometric deviation of the workpiece. This adjustment takes place depending on the previously determined deviation quantities, for example the said displacement vector fields. The first tool is adapted depending on an addition of all the following deviation variables based on the condition used as a basis in step a). In other words, the adjustment in step d) takes place starting from the effective surface of the first tool on which the simulation of the first shaping operation is based. If the first tool was configured as a zero tool, the adjustment in step d) takes place based on the zero geometry of the first tool. To put it simply, the effective surface of the first tool is “bent over”, which is equivalent to changing the geometry of the effective surface against the direction of the elastic springback. Methods suitable for this are generally known as such. These include, for example, the so-called displacement adjustment method and modifications of the same, as used in commercially available FEM software to simulate sheet metal forming processes. Also worth mentioning is the so-called “structural mechanical” compensation method, as described in the DE 10 2016 212 933 A1 is described. There is also a compensation method known as the Comprehensive Compensation (CC) method, which is recognized in the aforementioned German disclosure document. Against this background, a further description of the details of step d) is unnecessary. It is important to recognize that the adjustment of the at least one further tool in step e) only depends on the subsequent deviation variables - namely a deviation variable in a two-stage manufacturing process or i-1 deviation variables in an i-stage manufacturing process - starting from that in step b) underlying condition takes place.

In the final step z), the previously adapted effective surfaces of the tools are defined as the compensation geometry of the respectively represented pressing tool.

In an embodiment of the invention, steps f) to h) are provided according to the wording of claim 2, with their execution being carried out after step e) of the method according to claim 1. This embodiment of the invention is based on the consideration that the adaptation of the active surfaces - in order to minimize the geometric deviation of the workpiece determined in claim 1 - has an influence on the springback in the operations and thus also on the geometric deviation of the workpiece present at the end of the multi-stage pressing process Workpiece will have from the desired zero geometry. In contrast, the method according to claim 1 assumes that this influence will be negligibly small, so that a single adjustment of the effective surfaces is sufficient to obtain a dimensionally stable workpiece at the end of the multi-stage pressing process.

Step f), which is to be carried out immediately after step e), provides for continuous simulation of all pressing operations of the multi-stage pressing process. This simulation is carried out in a manner corresponding to step a) or step b), so that in order to avoid repetitions, reference is made to the relevant disclosure in connection with the statements on claim 1. However, the simulation is carried out using the previously adapted effective surfaces of the first and second tools. Continuous simulation means that the springback geometry present after the first pressing operation is inserted into the following pressing operation. In contrast, in the procedure according to claim 1, a non-resilient pressed part zero geometry was inserted into the following pressing operation. At the end of the simulated multi-stage pressing process, a further springback geometry of the workpiece will occur. This springback geometry can also be referred to as the current or current springback geometry.

The following step g) provides for the geometric deviation of the workpiece to be determined again. The desired zero geometry of the workpiece is compared with the now existing springback geometry of the workpiece and, depending on this comparison, a deviation size that is now present is determined. This deviation quantity now present will differ in magnitude from the sum of the deviation quantities determined in step c) and will preferably be smaller in magnitude than this.

Step h) provides for a new adjustment of the tools, namely the first tool and the at least one further tool, with regard to the geometric deviation of the workpiece that now exists. To avoid repetition, reference is made to the disclosure in connection with steps d) and e), which applies in a corresponding manner with regard to step h). The adjustment of the effective surfaces of the first and at least one further tool takes place in addition to the previously carried out geometric adjustments of the effective area.

Finally, the active surfaces adjusted again in this way can be defined as the compensated effective geometry of the respectively represented pressing tool in a manner corresponding to step z).

In a further embodiment of the invention it is provided that steps f) to h) are carried out iteratively, ie repeatedly. The repeated execution should be carried out until a predetermined number of iterations is reached and/or until a convergence criterion is reached. The convergence criterion can be assigned to the deviation size and/or the workpiece position error. With this embodiment of the invention, non-linear springback behavior can be taken into account. To put it simply, the effective surfaces of the tools are adjusted again and again, taking into account the adjustments that have already been made, until a satisfactory result is achieved with regard to the dimensional accuracy of the workpiece at the end of the multi-stage pressing process.

In a further embodiment of the invention, the method is based on a multi-stage pressing process with more than one subsequent operation. In contrast, the method in its simplest form only provides for a first pressing operation and a single further one, namely a second pressing operation and accordingly a first and a second tool. In the present embodiment, several further pressing operations, for example two, three, four, five or any number of pressing operations, are provided, which are simulated in a manner corresponding to step b) or step f). It is provided that the additional tool is adapted in a manner corresponding to step e), that is to say exclusively depending on the deviation variables that follow. Furthermore, it is provided that the additional tool is adjusted again in a manner corresponding to step h), that is, depending on the existing dimensional deviation at the end of the multi-stage pressing process.

In a further embodiment of the invention, simulating the pressing operations includes computer-aided calculation of the respective elastically resilient springback geometry of the workpiece using a nonlinear finite element method. In addition to the respective springback geometry, unspecified intermediate configurations of the workpiece, such as those that can occur when simulating the actual pressing process, can also be determined. An underlying finite element formulation can be formulated explicitly or implicitly. A nonlinear elastic-plastic material model is used to represent the elastic-plastic deformation behavior of the workpiece that occurs during press processing.

In a further embodiment of the invention, determining and/or re-determining the geometric deviation of the workpiece includes determining the existing deviation quantity in the form of a deviation vector field. The deviation vector field is formed by displacement vectors which extend between the zero geometry of the workpiece desired after the pressing operation in question and the elastically resilient springback geometry of the workpiece that actually exists after the pressing operation in question. The desired zero geometry can, for example, be in the form of a CAD target geometry, which is represented by a corresponding data record. Alternatively, if simulating the pressing operations involves application of a finite element method, the null geometry may be represented by a finite element mesh that represents a spatial discretization of the workpiece in the target null geometry. Accordingly, the springback geometry may be in the form of a deformed finite element mesh. In this case, the displacement vectors extend between one and the same node of the two finite element meshes.

In a further embodiment of the invention, adapting and/or re-adapting the effective surfaces to minimize the geometric deviation includes determining a correction geometry of the effective surface of the respective tool as a function of said deviation vector field. As mentioned at the beginning, the correction geometry can also be referred to as compensation geometry. This correction geometry can be determined in relation to a zero effective surface of the respective tool or in relation to an already existing adapted effective surface of the respective tool. Suitable methods for determining the correction geometry are generally known as such, in particular the displacement adjustment method, the so-called Comprehensive Compensation (CC) method and those in the published application DE 10 2016 212 933 A1 The “structural mechanical” method described can be mentioned. In simple terms, the correction geometry of the effective surface determined in this way represents an effective surface geometry that is “over-bent” in the direction opposite to the direction of the elastic springback. This over-bent geometry can be in relation to the zero tool, ie the zero effective surface, or in relation to an already present compensated state of the tool, ie an already existing adapted effective area can be determined.

The invention also relates to a method for producing a pressing tool with the features of claim 8. The pressing tool to be produced is intended for producing a pressed part by means of a pressing operation and may be intended, for example, for use in a drawing forming operation or a shaping or trimming operation. Accordingly, the pressing tool has an effective geometry for receiving and pressing the pressed part. In the method, the effective geometry of the pressing tool is first determined according to a method as described above. The pressing tool is then manufactured to form the determined effective geometry.

The invention also relates to a method for producing a pressed part, in which the pressed part is processed by pressing technology under the influence of a pressing tool produced according to the above-described method for producing a pressing tool.

The ability to carry out the methods according to the invention and their configurations can be implemented in the form of additional program parts, program modules and/or in the form of a program change to existing simulation software. Therefore, a further aspect of the present invention relates to a computer program product, in particular stored on a computer-readable medium or implemented as a signal, the computer program product - when loaded into a memory of a suitable computer and executed by the computer - causing the computer to do a Carrying out a method according to the invention and/or an embodiment of the invention.

BRIEF DESCRIPTION OF DRAWINGS

• 1 zeigt eine schematisch vereinfachte Darstellung zur Verdeutlichung eines im Stand der Technik bekannten Verfahrens zur Ermittlung rückfederungskompensierter Wirkflächen von Presswerkzeugen,
• 2 in einer der 1 entsprechenden Darstellungsweise ein weiteres im Stand der Technik bekanntes Verfahren gleichen Zwecks,
• 3 in einer der 1 entsprechenden Darstellungsweise nochmals ein weiteres im Stand der Technik bekanntes Verfahren gleichen Zwecks,
• 4 eine schematisch vereinfachte Darstellung zur Verdeutlichung einer Ausführungsform des erfindungsgemäßen Verfahrens zur Ermittlung rückfederungskompensierter Wirkgeometrien für Presswerkzeuge,
• 5a, 5b eine weitere Ausführungsform des erfindungsgemäßen Verfahrens zur Rückfederungskompensation ähnlich dem Verfahren nach 4, wobei Nichtlinearitäten berücksichtigt werden,
• 6 eine weitere Ausführungsform des erfindungsgemäßen Verfahrens zur Rückfederungskompensation ähnlich dem Verfahren nach 4, wobei ein zugrundeliegender mehrstufiger Pressprozess mehrere Folgeoperationen aufweist,
• 7 eine schematisch stark vereinfachte perspektivische Ansicht eines mittels einer Abfolge mehrerer aufeinanderfolgender Pressoperationen herzustellenden Pressteils, wobei ein entlang einer Schnittlinie A-A durch das Umformteil erstreckter Schnitt dargestellt ist, und
• 8 eine Rückfederungsgeometrie und zugehörige Nullgeometrie des Werkstücks sowie ein sich zwischen beiden Geometrien erstreckendes Abweichungsvektorfeld.

Further advantages and features of the invention result from the claims and from the following description of preferred exemplary embodiments of the invention, which are shown with reference to the drawings.

• 1 shows a schematically simplified representation to illustrate a method known in the prior art for determining springback-compensated effective surfaces of pressing tools,
• 2 in one of the 1 corresponding representation, another method known in the prior art for the same purpose,
• 3 in one of the 1 corresponding representation, another method known in the prior art for the same purpose,
• 4 a schematically simplified representation to illustrate an embodiment of the method according to the invention for determining springback-compensated effective geometries for pressing tools,
• 5a , 5b a further embodiment of the method according to the invention for springback compensation similar to the method according to 4 , where non-linearities are taken into account,
• 6 a further embodiment of the method according to the invention for springback compensation similar to the method according to 4 , whereby an underlying multi-stage pressing process has several subsequent operations,
• 7 a schematically greatly simplified perspective view of a pressed part to be produced by means of a sequence of several successive pressing operations, a section extending along a section line AA through the formed part being shown, and
• 8th a springback geometry and associated zero geometry of the workpiece as well as a deviation vector field extending between both geometries.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Some exemplary embodiments are explained below to explain possible ways of implementing the invention in practice. The methods according to the invention presented serve for a computer-aided, simulation-based determination of spring-back-compensated effective geometries for pressing tools that are intended for producing a pressed part by means of a sequence of several successive pressing operations. This sequence of pressing operations can also be referred to as a multi-stage pressing process. To put it simply, the methods according to the invention can also be referred to as methods for (computer-aided, simulation-based) springback compensation. In this context, springback compensation is to be understood as an adaptation of the effective surfaces of virtual tools, whereby the adaptation is intended to compensate for inevitably existing elastic springbacks of the pressed part to be produced. The effective surfaces of the virtual tools compensated in this way serve as specifications for the production or specification of corresponding real pressing tools or the effective geometries of these pressing tools.

To illustrate the advantages and features of the method according to the invention, three methods for simulation-based springback compensation that are already known in the prior art will be discussed below schematically using the 1 until 3 are shown. First of all, the 1 until 3 The underlying schematic representation is explained in more detail, since this representation is also related to the method according to the invention 4 until 6 underlying.

The representation on which the figures in question are based can basically be read from left to right and from top to bottom and illustrates the respective process sequence in a very simplified manner against the background of a multi-stage pressing process. The 1 until 3 This is based on a pressing process with a total of two operations OP1 and OP2. In the present case, operation OP1 is a drawing forming operation and operation OP2 is a further subsequent operation (shaping and/or trimming operation), in which the workpiece previously formed using drawing technology is further processed in the direction of a desired target configuration. In the schematic representations, the cross-shaped drawing elements refer to an existing geometry of the workpiece, which is shown in relation to a dashed zero line. This zero line represents a target geometry of the workpiece that is desired after the respective operation, which can also be referred to as zero geometry. The circular drawing elements refer to a geometry of the (virtual) tool to be used in the respective operation. These tools each represent a real pressing tool to be used in the relevant (real) operation. The circular drawing elements refer to the effective surface geometries of the tools. The respective effective surface geometry, or effective surface for short, is shown in the schematic representations in relation to a tool zero geometry, which in turn is illustrated by the dashed reference line. Everything else becomes clear from the following description.

This is what the method known in the prior art looks like 1 To put it simply, first a computer-aided simulation of the multi-stage pressing process in an uncompensated state of the respective tools (basic simulation). Uncompensated means that the tools are in their zero geometry, so that the tools can also be referred to as “zero tools”. These “zero tools” are based on a CAD target geometry of the workpiece to be produced, so that the (uncompensated) effective surfaces of the tools are geometrically identical to the desired zero geometry of the workpiece. More precisely, the first operation OP1 is first simulated, with the virtual workpiece being elastically and plastically formed using a first tool on which the first operation is based. In any case, when the first tool is closed, there is no elastic springback of the workpiece. This only occurs after the tool has been opened and/or the workpiece has been removed from it.

The elastic springback (SB1_Basic) of the workpiece is illustrated by the positioning of the cross-shaped drawing element, which is shifted upwards in relation to the dashed reference line between operations OP1 and OP2. The result of this springback is a geometric deviation (A1_Basic) whose final state is represented by the springback geometry (G1_Basic). Starting from this state (G1_Basic), the workpiece is further processed in operation OP2 using another tool. When the hold-down device(s) of this tool is closed, the workpiece inevitably deforms elastically or elastic-plastically, starting from the elastically spring-back configuration (G1_Basic), due to the workpiece position error (L1_Basic) corresponding to the deviation (A1_Basic). Here, elastic energy is introduced into the workpiece, which is represented by the hatched triangle in the illustration 1 is represented. After simulating the operation OP2 and removing it from the relevant tool of OP2, the workpiece assumes a further configuration (G2_Basic), which deviates from the desired zero geometry at the end of the multi-stage pressing process due to springback. This undesirable geometric deviation (A2_Basic) is illustrated by the vertically extended double arrow drawn after operation OP2 between the dashed reference line of the zero geometry and a horizontal reference line with respect to the cross-shaped drawing element.

The known method is used to compensate for these geometric deviations 1 a fundamentally known “overbending” of the first tool of OP1. This is illustrated by the positioning (-A2_Basic) of the relevant effective surfaces (circular drawing elements) that now deviates downwards from the dashed reference line. With this compensation strategy, however, when the workpiece is inserted into the tool of the OP2, a non-optimal workpiece position results, characterized by the workpiece position error (L1_1). This non-optimal workpiece position leads to an unwanted elastic deformation of the workpiece when the tool is closed, so that the non-optimal workpiece position is also represented by the hatched triangle. This is because the OP2 tool is not taken into account in this compensation strategy, so that it still exists in its zero geometry. Although the basis is used 1 clarified well-known compensation strategy at the end of the As assumed, a dimensionally stable workpiece is achieved during the molding process. However, the previously mentioned non-optimal workpiece position is not taken into account when inserting the workpiece into the additional tool of the OP2. However, the repeatability of the pressing process can be impaired due to the non-optimal workpiece position in the OP2 due to springback. In addition, the representation of the 1 and 2 that the non-optimal workpiece position can have an influence on the geometric deviation of the workpiece after OP2. This is due to prevailing non-linearities, which are included in the for the purpose of easier clarification 1 and 2 were neglected.

Another compensation strategy known in the art is based on 2 clarified. In this process, too, a computer-aided simulation of the multi-stage pressing process is first carried out using zero tools. The resulting geometric deviation of the workpiece at the end of the pressing process (A2_Basic) is - as in the process 1 - used to compensate for the OP1 tool. In addition, the tool of the OP2 is also compensated depending on the previously determined geometric deviation (A2_basis), which is illustrated by the positioning of the effective surface of the OP2 (circular drawing element there) that deviates from the dashed reference line. Here too, due to the elastic springback of the workpiece after OP1 (SB1_1), there is a non-optimal workpiece position in OP2 (L1_1). Accordingly, even with this known method, there is no optimal workpiece position either before or after compensation of the tools of the pressing operations OP1 and OP2, which in turn is illustrated by the hatched triangle.

In comparison to the known method 1 would be the well-known procedure 2 comparatively more advantageous for the multi-stage pressing process shown here with the existing deviations. The workpiece position in the OP2 is determined by compensating for the geometric deviations in the process 2 Assumedly not influenced in terms of type and extent, which can be seen from the constant shape of the hatched triangle. Assuming that a change in the workpiece position - due to prevailing non-linearities in the 1 and 2 are neglected - the dimensional accuracy of the workpiece is influenced at the end of the pressing process, is the known method 2 therefore comparatively more advantageous.

Nevertheless, what these two known compensation strategies have in common is that the compensation only takes place with regard to the geometry of the workpiece at the end of the pressing process. However, the position of the elastically spring-backed workpiece when it is picked up in or on the respective tools of the pressing operations is not taken into account.

In addition to the two methods shown, there is another method in the prior art 3 known. This process takes the position of the workpiece into account. As before, the procedure will be demonstrated using a two-stage pressing process. Initially, only the first forming operation (OP1) with a zero tool and the subsequent springback (SB1_0) of the workpiece are simulated here. The tool effective surface of the following, receiving operation (OP2) is then adapted at least in sections to the incoming, spring-back workpiece. The incoming workpiece (G1_0) is picked up and further processed on the adapted tool effective surface (W2_0*). The spring-back workpiece geometry (G2_0) that occurs after this operation is then calculated. The dimensional deviation (A2_0) at the end of the multi-stage process between the spring-back workpiece geometry and the zero geometry is now used to compensate for the effective area of the first operation against the dimensional deviation (-A2_0). The first operation with the compensated effective surface (W1_1) and the subsequent springback (SB1_1) of the workpiece are then simulated. The effective surface of the second operation is then adapted to the existing workpiece geometry (G1_1). With the effective surface (W2_1) adjusted in this way, the workpiece is picked up and further processed. The springback of the workpiece (SB2_1) is then calculated again. Assuming that the compensation or adjustment of the effective surfaces has no influence on the springback, a dimensionally stable workpiece is now achieved at the end of the pressing process. Furthermore, by adapting the receiving effective surfaces of the second operation (OP2), an assumedly very good workpiece position is achieved when inserted into it. If this assumption does not apply and there are still dimensional deviations at the end of the multi-stage pressing process, the procedure can be repeated in further iterations.

Compared to the first two methods described above, the invention is based on the consideration that neglecting the workpiece position in the springback compensation leads to a deterioration in the repeatability of the multi-stage pressing process with regard to the resulting elastic springback of the workpiece can lead. In addition, the invention is based on the consideration that neglecting the workpiece position during springback compensation - depending on the prevailing influence of the workpiece position on the resulting geometric deviations at the end of the pressing process - can lead to a compensation result that meets the requirements not being able to be achieved. This means even after a possible multiple iterative iteration of the compensation strategies 1 and 2 The compensation geometries or compensated tools determined in this way do not guarantee that a dimensionally accurate pressed part can be produced.

In comparison with the third method described above (partial position-optimized compensation), the workpiece position is also taken into account in all operations in the invention. However, not by adapting the effective surfaces of the individual operations to the geometry of the incoming workpiece, but rather by the fact that the incoming workpiece is, by definition, in its respective zero configuration - i.e., as assumed, free of springback up to this point. Since the geometry of the incoming workpiece is identical to the effective surface of the receiving tool, no elastic energy is introduced into the workpiece when the hold-down device(s) is closed. There is also no workpiece position error.

Against this background, the invention presents this on the basis of 4 until 6 clarified methods for springback compensation.

It has been shown that the method according to the invention (as well as that in 3 clarified procedures according to the disclosure document DE 10 2019 203 082 A1 2020.09.10) and its refinements have the most general applicability possible to differently designed multi-stage pressing processes and enable the production of pressing tools for use in such multi-stage pressing processes, these pressing tools being designed in such a way that the pressed parts produced with them have very good dimensional accuracy and at the same time very good Have repeatability.

Based on that 4 In the illustrated example of the method according to the invention for springback compensation, there is a multi-stage pressing process with a sequence of several consecutive pressing operations OP1 and OP2. In this example, operation OP1 is a drawing forming operation and operation OP2 is a shaping and/or trimming operation in which the workpiece previously formed using drawing technology is further processed.

It is important to note that the multi-stage pressing process used here - as well as the following ones 5a until 6 underlying multi-stage pressing processes - is to be understood purely as an example. The explained methods according to the invention are, independent of the exemplary pressing processes used here, also applicable in particular to other multi-stage pressing processes with different and/or additional pressing operations.

In step a), the method initially involves simulating the first pressing operation OP1. A (virtual) workpiece (circuit board) is picked up on an active surface (W1_0) of a first tool, which represents a first pressing tool, and is elastically and plastically formed. When the first tool is closed, the tool and workpiece geometry are inevitably identical. After opening the first tool, an elastically spring-back first spring-back geometry (G1_0) of the workpiece results.

The simulation of the operation OP1 and the determination of the elastic springback geometry (G1_0) is carried out in this case computer-aided and simulation-based using a nonlinear finite element method. Such methods are well known in the area of the virtual design of components and/or processes, so the relevant details will not be discussed further.

The method then provides for simulating the at least one further pressing operation OP2 in step b). However, it is not the elastically spring-back spring-back geometry (G1_0), but rather the non-spring-back pressed part zero geometry (G1_0*) that is inserted into the tool, picked up on the active surface (W2_0) of the second tool and elastically-plastically formed and/or trimmed. The workpiece is picked up on the effective surface W2_0 in the most accurate manner possible due to the at least partially identical geometry of the tool effective surface and the workpiece, so that when the hold-down device(s) is closed, no or only very little elastic energy is introduced into the workpiece . Simulating b) the OP2 also includes determining the existing elastically spring-backed further spring-back geometry G2_0 of the workpiece (after opening the tool in question). In the present case, the springback geometry G2_0 deviates from the desired zero geometry N, which is based on 4 is illustrated in the upwardly shifted positioning of the springback geometry G2_0.

The procedure according to 4 According to this, the geometric deviations A1_0 and A2_0 of the workpiece are determined, whereby on the one hand the springback geometry G1_0 present after OP1 and on the other hand the springback geometry G2_0 present after OP2 are each compared with the desired zero geometry N and two deviation sizes are determined depending on these comparisons .

In the present case, determining c) the geometric deviation A1_0 or A2_0 includes determining the respective deviation size in the form of a deviation vector field. The deviation vector field is formed by displacement vectors that extend between the desired zero geometry N of the workpiece and the existing springback geometry G1_0 or G2_0 of the workpiece.

The procedure looks like this 4 an adapting d) of the first tool on which OP1 is based and an adapting e) of the further tool on which OP2 is based. More precisely, in step d), the effective surface W1_0 of the first tool is “bent” depending on the sum of the geometric deviations A1_0 and A2_0 so that an adapted effective area W1_1 results. In the present case, the effective surface W1_0 represents a zero geometry of the first tool. The corresponding circular drawing element of the 4 is positioned on the said dashed reference line. The adjustment e) of the further tool is carried out in a corresponding manner, with the effective surface of the further tool W2_0 only being adapted depending on the deviation A2_0. This results in a now adapted effective area W2_1 of the tool of operation OP2. When using tools adapted in this way, it is assumed that, on the one hand, a workpiece can be produced within the required dimensional tolerances and, on the other hand, the elastic energy when closing the hold-down device(s) in OP2 can be greatly reduced, ideally completely eliminated.

In the present case, adjusting d) and adjusting e) of the corresponding effective surfaces to minimize the geometric deviations A1_0 and A2_0 of the workpiece includes determining an unspecified correction geometry of the relevant effective surface depending on the deviation vector fields previously determined in step c) between the springback geometries G1_0 and G2_0 and the zero geometry N of the workpiece. The correction geometries W1_1 and W2_1 are determined in relation to their respective zero effective area. Methods suitable for this are generally known as such in the prior art, in particular the displacement adjustment method (method of inverse vectors), the comprehensive compensation (CC) method or that in the published application DE 10 2016 212 933 A1 learned method can be mentioned. Against this background, it is unnecessary to explain further details of the adjustments to the effective surfaces to be made in steps d) and e).

The effective surfaces W1_1 and W2_1 adapted in this way can then be defined as the springback-compensated effective geometry of the real pressing tool represented. This means that when producing such a pressing tool, a corresponding geometric specification of the pressing tool is determined based on the previously adapted effective surfaces W1_1 and W2_1 and its effective geometry is manufactured accordingly.

Further embodiments of the method according to the invention are based on 5a until 6 clarified. The procedures clarified there are consistent with the method in terms of their characteristics and in particular the steps to be carried out and their design 4 clarified procedures. Identical and/or corresponding process features and/or process steps are provided with identical reference numerals. To avoid repetition, identical and/or corresponding process features and/or process steps are not explained separately for each embodiment. Rather, only the essential differences between the individual exemplary embodiments will be discussed. With regard to consistent process features and/or process steps, reference is made to the process according to 4 related disclosure.

This based on the 5a and 5b Illustrated method according to the invention for springback compensation essentially differs from the method according to 4 that the influence of adjusting the tools to compensate for the dimensional deviations has an influence on the springback amounts (SB1_1 # SB1_0; SB_2_1 # SB2_0) and thus results in a geometric deviation of the workpiece at the end of the pressing process. To compensate for this deviation that now exists, the method provides further steps f) to h), which immediately follow step e), namely the adjustment of the at least one further tool of OP2.

This being said, the procedure looks like this 5a and 5b a step f) in which the complete multi-stage pressing process is simulated. The simulation is carried out in a manner corresponding to step a) or step b). However, the springback geometry of the workpiece G1_1 present after step a) is transferred directly to the second tool of OP2 - and not in a springback-free configuration as before. This simulation - in contrast to step a) or step b) - is also based on the previously adapted effective surfaces W1_1 and W2_1. Due to the adjustments made to the effective surfaces, a different springback amount initially results after the first operation OP1 (SB1_1 # SB1_0). This leads to a workpiece position error L1_1 when recording the spring-back workpiece geometry G1_1 on the effective surface W2_1 of the tool in OP2, which in turn leads to elastic energy (represented by the hatched triangle) in the workpiece when the tool's hold-down device(s) is closed . The adaptation of the effective surface in OP2 now leads, in conjunction with the elastic energy described, to a different springback amount (SB2_1 # SB2_0) and a new springback geometry of the workpiece G2_1 results at the end of the pressing process, which is still outside the required dimensional tolerances.

After this, in step g), the geometric deviation of the workpiece that is now present is determined again in a manner corresponding to step c). Accordingly, a springback geometry G2_1 that is now present after OP2 is compared with the desired zero geometry N and, depending on this comparison, a deviation quantity (A2_1) that is now present is determined. The deviation size is also determined here in the form of a deviation vector field, which is not shown in the drawing.

Thereafter, in a manner corresponding to step d) or step e), the first and at least one further tool are adjusted again h) in order to minimize the geometric deviation of the workpiece from the zero geometry N. In contrast to steps d) and e) However, both already adapted effective surfaces W1_1 and W2_1 are further adapted depending on the dimensional deviation now present at the end of the process (A2_1), to compensate for this geometric deviation, or in accordance with the method 3 correspondingly further “bent over” (-A2_1).

The effective surfaces of the tools of OP1 (W1_2) and OP2 (W2_2) determined in this way can be defined as the springback-compensated effective geometry of the real pressing tool represented.

Alternatively, you can - as shown below 5b apparent - a repeated, iterative execution of process steps f) to h) may be provided. In the present case, a further iteration (ie a total of two iterations) is provided, with the first execution through the first display line, the first iteration through the second display line and the second iteration through the third line of the 5b should be clarified. As part of the initial execution, when f) the complete multi-stage pressing process is simulated again, the now existing elastically spring-back geometry G2_1 of the workpiece is determined. By comparing the springback geometry G2_1 with the desired zero geometry N in step g), the now present deviation A2_1 results. The underlying tools are adapted in step h) in a first iteration, ie the effective surfaces W1_1 and W2_1 are further “bent over” so that the effective surfaces W1_2 and W2_2 are then present. This is followed by a further run through steps f) to h), taking into account the effective surfaces W1_2 and W2_2 of the tools, whereby the springback geometry G2_2 is determined. By comparing the springback geometry G2_2 with the desired zero geometry N in step g), the deviation A2_2 that now exists results. The underlying tools are adjusted again in a second iteration in step h), that is, the effective surfaces W1_2 and W2_2 are further “bent over” so that the effective surfaces W1_3 and W2_3 are then present. Based 5b It should be made clear that after the previously described repeated run, ie a further iteration (which can also be referred to as a “compensation loop”), there is no longer any significant geometric deviation of the workpiece at the end of the multi-stage pressing process. Rather, as expected, the workpiece assumes the zero geometry desired according to OP2.

The effective surfaces W1_3 and W2_3 determined in this way can be defined as the springback-compensated effective geometry of the real pressing tool represented.

The based 6 In contrast to the previously described methods, the illustrated embodiment of the method according to the invention provides for several further pressing operations, each with an additional tool. In the present case, instead of a further pressing operation OP2, two further pressing operations OP2 and OP3 are provided. The adjustment and/or re-adjustment of the respective additional tool takes place depending on the following deviation variables. In detail:

The procedure according to 6 First sees a simulation of a) the OP1 with a zero tool geometry representing effective surface W1_0. Here, the elastically spring-back geometry G1_0 of the workpiece is determined.

The first further pressing operation OP2 is then simulated in a first step b). However, it is not the elastically spring-back spring-back geometry G1_0, but rather the non-spring-back pressed part zero geometry G1_0* that is inserted into the tool of OP2, picked up on the effective surface W2_0 and elastically-plastically formed and/or trimmed. This first step b) also includes determining the elastically spring-back further spring-back geometry G2_0 of the workpiece that is present (after opening the tool).

A second step b) is then carried out in a manner corresponding to the first step b). The non-rebound pressed part zero geometry G2_0* is inserted into the tool of the OP3, picked up on the effective surface W3_0 and elastically plastically formed and/or trimmed. As before, this second step b) also includes determining the elastically spring-back further spring-back geometry G3_0 of the workpiece (after opening the tool).

The geometric deviations between the springback geometries G1_0, G2_0 and G3_0 and the desired zero geometry N are then determined in a step c). This results in the deviations A1_0, A2_0 and A3_0.

The first tool is then compensated depending on the sum of all deviation variables (A1_0+A2_0+A3_0) in a manner corresponding to step d), with an adapted effective surface W1_1 being determined.

The tools underlying the two further pressing operations OP2 and OP3 are also adapted accordingly. The adjustment is carried out in a manner corresponding to step e). It is important to recognize that the effective area of the first further pressing operation OP2 is only adjusted depending on the sum of the following deviation variables A2_0 and A3_0. Accordingly, the adjustment of the second further pressing operation OP3 only takes place depending on the subsequent deviation variable A3_0. The adapted effective areas W2_1 and W3_1 are determined here.

It goes without saying that this is also based on 6 clarified procedures for taking prevailing non-linearities into account using the 5a and 5b can be iteratively carried out and/or designed in a manner corresponding to the illustrated method.

7 shows a pressed part S` which is produced by means of a sequence of several consecutive pressing operations. The pressed part S` is in the present case designed in the form of a body component for a passenger car made of sheet steel. The multi-stage pressing process intended for producing the pressed part S` has a first pressing operation OP1 and a further pressing operation OP2. Continues to show 7 a sectional view through the two tools Z1 and Z2, which are used to produce the in 7 Pressed part S` shown are provided. The tools are each shown in the closed state and act on the workpiece S with their respective effective surfaces.

8th shows a springback geometry (Gx_x) and associated zero geometry (N) of the workpiece as well as a deviation vector field (U) extending between both geometries.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102019203082 A1 [0009, 0013, 0046]
• DE 102019203082 [0010]
• DE 102016212933 A1 [0017, 0028, 0055]

Claims (10)

Computer-aided method for determining spring-back-compensated effective geometries for pressing tools that are intended for producing a pressed part (S`) by means of a sequence of several consecutive pressing operations (OP1, OP2), with the steps: a) Simulating a first pressing operation (OP1) of the sequence, wherein a workpiece (S) representing the pressed part (S`) is picked up on an active surface (W1_0) of a first tool (Z1), which represents a first pressing tool, and is elastically-plastically formed is, and wherein a subsequent elastically spring-back first spring-back geometry (G1_0) of the pressed workpiece (S) is determined; b) Simulating the at least one further pressing operation (OP2) of the sequence, whereby the previously pressed workpiece (S) must be in a non-spring-back configuration (pressed part zero geometry) (G1_0*), in order to minimize the workpiece position error (L1_Basic), and on the effective surface (W2_0) of the second tool (Z2) is picked up and elastically-plastically formed, and a subsequent elastically spring-back further spring-back geometry (G2_0) of the workpiece (S) is determined; c) determining the geometric deviations (A1_0, A2_0) of the workpiece (S), whereby the desired zero geometry (N) of the workpiece (S) is compared with the respective elastically resilient springback geometries (G1_0, G2_0); d) Adjusting the first tool (Z1), the effective surface (W1_0) of the first tool (Z1) being adjusted to minimize the geometric deviations (A1_0, A2_0) of the workpiece (S) depending on an addition of all the following deviation variables (A1_0, A2_0). becomes; e) adapting the at least one further tool (Z2), the effective surface (W2_0) of the at least one further tool (Z2) only being adapted depending on the subsequent deviation size (A2_0), and z) Determining the adapted effective surfaces (W1_1, W2_1) of the tools (Z1, Z2) as springback-compensated effective geometries of the respectively represented pressing tool. Computer-aided procedure Claim 1 , wherein following step e): f) all pressing operations of the sequence (OP1, OP2) are simulated with the effective surfaces (W1_1, W2_1) adapted in step d) and e); g) re-determining the geometric deviation (A2_1) of the spring-back workpiece (S), comparing the desired zero geometry (N) of the workpiece with the elastically spring-back spring-back geometry (G2_1) at the end of the sequence; h) adjusting the tools (Z1, Z2) again, whereby the effective surfaces (W1_1, W2_1) that were already adjusted in steps d) and e) are further adjusted depending on the dimensional deviation (A2_1) that is now present. Computer-aided procedure Claim 2 , in which, in order to take prevailing non-linearities into account, it is provided that steps f) to h) are carried out iteratively until a specified number of iterations is reached and / or until a convergence criterion assigned to the deviation size is reached. Computer-aided method according to one of the preceding claims, wherein several further pressing operations (OPx, e.g. OP3, OP4) are provided, each with a further tool (Zx, e.g. Z3, Z4), wherein: the simulation takes place according to step b); the geometric deviations are determined according to step c); the adjustment takes place according to step e); the new adjustment takes place according to step h). Computer-aided method according to one of the preceding claims, wherein simulating the pressing operations comprises computer-aided calculation of the respective elastically resilient springback geometry (Gx_x, e.g. G1_0, G1_1, G2_0) of the workpiece (S) using a nonlinear finite element method. Computer-aided method according to one of the preceding claims, wherein determining and/or re-determining the geometric deviation (Ax_x, e.g. A1_0, A1_1, A2_0) of the workpiece (S) comprises the steps: determining the existing deviation quantity in the form of a deviation vector field (U ), which is formed by displacement vectors that extend between the desired zero geometry (N) of the workpiece (S) and the existing springback geometry (Gx_x, e.g. G1_0, G1_1, G2_0) of the workpiece (S). Computer-aided procedure Claim 6 , wherein adjusting and/or readjusting the effective surfaces to minimize the geometric deviation (Ax_x, e.g. A1_0, A1_1, A2_0) of the workpiece (S) includes the steps: Determining a correction geometry of the effective surface of the respective tool (Z1, Z2) as a function of the deviation vector field (U), the correction geometry being determined in relation to a zero effective surface (N) of the respective tool (Z1, Z2) or in relation to an already existing adapted effective surface of the respective tool (Z1, Z2). Method for producing the pressing tools, which are intended for producing a pressed part (S`) by means of several pressing operations (OPx, e.g. OP1, OP2,), wherein the pressing tools (Zx, e.g. Z1, Z2) each have an effective geometry for receiving and/or pressing technology Editing (forming and/or trimming) of the pressed part (S`), with: determining the effective geometries according to a computer-aided method according to one of the preceding claims; Manufacture of the pressing tools using the determined effective geometries. Method for producing a pressed part (S`), in which the pressed part (S`) is under the influence of the according to the method Claim 9 manufactured pressing tools are processed using press technology. Computer program product, which is in particular stored on a computer-readable medium or implemented as a signal, wherein the computer program product - when loaded into a memory of a suitable computer and executed by the computer - causes the computer to carry out a method according to one of Claims 1 until 7 executes.